Lawful interception of data traffic, such as telephone calls that travel through a communications network, occurs for law enforcement purposes such as crime prevention, surveillance, public safety, or evidence gathering. Communications networks normally include a centralized core network, implementing a control layer, associated with non-core networks such as access and aggregation networks, which provide connectivity between end users as well as between end users and the core network. Examples of the latter are broadband networks, which are located between the core network and the end users.
Lawful interception equipment allows interception or third party monitoring of data traffic traveling through the network. To enable interception, this equipment is located in nodes in those portions of the network where the traffic actually flows. For example in the IP Multimedia Subsystem architecture, all data traffic flows through a few, well defined centralized locations, and the interception of this data traffic takes place in the elements located at these locations within the centralized, or core, portion of the communications network. In this case the core network includes logic elements that enable data traffic to be intercepted and routed to an authorized entity.
This centralized form of lawful traffic interception is not without its drawbacks. For example, evolving network architectures allow broadband traffic to pass between users without necessarily passing through centralized equipment associated with the core network. Because the lawful interception equipment is only located in nodes in the core network, a problem arises when data traffic partially or completely passes from a caller to a recipient without passing through these nodes located in the centralized core network. Existing interception technologies that are designed to intercept voice communications through a telephone network are located within the centralized core network elements and are bypassed by decentralized traffic transmissions such as peer to peer type transmissions that do not pass through elements responsible for interception. Traffic that flows in this manner can therefore not be intercepted.
Furthermore, as telecommunications networks evolve, new multimedia services and applications have been made available to users. Many of these services are more than standard voice communications, such as file sharing, video streaming or other types of broadband applications. Since existing interception technologies were designed for intercepting traffic such as voice communications with a limited bandwidth of approximately 64 kbps, they are not robust enough to properly intercept or transfer traffic that is transmitted not only in a less centralized manner but also in different formats that have higher bandwidths than audio signals spoken over a telephone. Furthermore, existing lawful interception systems are not scalable enough to transmit these higher bandwidths.